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Juan Crespo
Juan Crespo, ASE Certified Technician
Category: Jeep
Satisfied Customers: 1526
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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2002 liberty 3.7 warm heat 85degrees new stat water pump

Customer Question

2002 liberty 3.7 warm heat 85degrees new stat water pump radiator heater core hoses hot blend works is there more than one blend door
Submitted: 1 year ago.
Category: Jeep
Expert:  Juan Crespo replied 1 year ago.

Hi there. Welcome to our site.

There is only one blend door; however, if the recirculation door is open and allowing cold fresh air to come in, depending on how cold the outside air is, cab temperatures might not be as warm as the setting indicates. Unless you have Automatic air, all the actuators work with vacuum and can be tested with a vacuum gauge - see attached graphic for test table.

Please let me know if you have any other questions.

Best Regards.

Customer: replied 1 year ago.
I manually shut the recurculation door and kept it shut i picked up a few degrees but nothing close to what it should be.. My brothers Liberty05 puts out on defrost 140 degrees.
Expert:  Juan Crespo replied 1 year ago.

Heater temperature output should be the same for your Liberty as it is for your brother's. If the recirculation door was not the main cause of the insufficient heat issue, we'll need to compare normal operating engine temperature and thermostat specifications between the two vehicles. If those are the same, chances are then that the problem with your Jeep is being caused by a partially clogged heater core, in which case a good chemical flush and fresh coolant should solve the problem.

Please let me know if you have any other questions.

Best Regards.

Customer: replied 1 year ago.
both vehicles have oem stats my hoses going in and out of core are much hotter than my brothers. i have flushed core twice, so far you havent anwsered or provided me with anything i havent tried
Expert:  Juan Crespo replied 1 year ago.

I'm here to help you. I'm sorry if you were expecting something other than a thorough revision of the issue, so please don't worry about paying me for my time.

Back to the issue, inlet heater hose should be hotter than outlet having gone through the heater core. If both hoses are at the same temperature, then check for a possible air bubble left in the system impeding circulation after flushing the heater core. If that's the case, here is the procedure for filling the system up:


  • Tighten the radiator draincock and the cylinder block drain plug(s) (if removed).

CAUTION: Failure to purge air from the cooling system can result in an overheating condition and severe engine damage.

  • Fill system using a 50/50 mixture of ethylene glycol antifreeze and low mineral content water. Fill pressure bottle to service line and install cap.

NOTE: The engine cooling system will push any remaining air into the coolant bottle within about an hour of normal driving. As a result, a drop in coolant level in the pressure bottle may occur. If the engine cooling system overheats and pushes coolant into the overflow side of the coolant bottle, this coolant will be sucked back into the cooling system ONLY IF THE PRESSURE CAP IS LEFT ON THE BOTTLE. Removing the pressure cap breaks the vacuum path between the two bottle sections and the coolant will not return to cooling system.

  • With heater control unit in the HEAT position, operate engine with pressure bottle cap in place.
  • Add coolant to pressure bottle as necessary. Only add coolant to the pressure bottle when the engine is cold. Coolant level in a warm engine will be higher due to thermal expansion.

NOTE: The coolant bottle has two chambers. Coolant will normally only be in the outboard (larger) of the two. The inboard chamber is only to recover coolant in the event of an overheat or after a recent service fill. The inboard chamber should normally be empty. If there is coolant in the overflow side of the coolant bottle (after several warm/cold cycles of the engine) and coolant level is above cold full when cold, disconnect the end of the overflow hose at the fill neck and lower it into a clean container. Allow coolant to drain into the container until emptied. Reconnect overflow hose to fill neck.

Another possibility could be a combustion chamber leak from a bad head gasket allowing gases into the cooling system. To test that possibility, you could borrow a block tester kit from any of the major auto parts retailers.

Once again, my goal is to help you solve your issue, everything else is secondary.

Best Regards.

Customer: replied 1 year ago.
I have done all of the following when it came to purging air from system. I have also loosed the bleed valve by the upper hose. if the vehicle had a bad head gasket wouldnt the car overheat plus i would suspect I would loose coolant and have white smoke coming from exhaust. coolant level is right on, temp rides in the middle will try another bleed tomorrow. I am going to look at other door issues. the two mechanics at work believe it to be a door issue but which one they dont know. like i said I cut an access hole in heater box and can see blend door open and close. There was a guy on you tube several years ago, that had same issue, but never reposted if he ever solved his problem. Listed under liberty with no heat, he also cut his heater box. Oil looks fine, would suspect coolant if head gasket, also if air in system,i would expect an overheat. but no such thing. I was a certified ASE mechanic for 25 years, but do other things now. This has me stumped.
Expert:  Juan Crespo replied 1 year ago.

After reading your last post, I agree with you that it doesn't look like there is a problem with a head gasket as it would loose coolant for sure.

With the engine running at normal temperatures, plus you shutting off the recirculation door manually and watching the blend door work as it should, and adding the fact that both heater hoses are at the same temperature coming out of the firewall, the only logical possibility I can think of is that of an air bubble causing all this grief.

Please let me know what happens after you bleed the system tomorrow.

Best Regards.

Customer: replied 1 year ago.
bled system again no change. cut access hole on right side of heater box to see front of blend door. it looks like the arm rests on the door when it shuts. any idea where i can find a picture of what the door should look like when closed?
Expert:  Juan Crespo replied 1 year ago.

I'm afraid Jeep doesn't give much detail about the HVAC air distribution scheme. Please take a look at the atached graphic and tell me if it helps.

Best Regards.